Banning contemptible viewpoints isn't going to stop anyone from having them. In fact, it may just provoke a further hardening of those beliefs, and perhaps even a violent reassertion of them by their adherents.

On Wednesday it was reported that David Cameron is to introduce new plans to crack down on non-violent "extremism". These plans will be detailed in the new Tory government's first Queen's Speech on the 27th of May, but we already know they'll include new immigration rules; powers to outlaw groups that seek to "undermine democracy"; "extremism disruption orders" for organisations that use hate speech in public places; and "closure orders" to shut mosques used by extremist clerics. The proposals were first set out by Home Secretary Theresa May before the general election, but didn't see the light of day because of opposition from the Liberal Democrats.

These plans, in my opinion, are bullshit. It is not the government's job to police how its citizens think or speak. There are, of course, limits to free speech – inciting violence, for example, is a criminal offence, and people who do this should be charged and punished. Causing offence to others, however, is not a criminal offence, and shouldn't be one. But even here there are limits, and those who offend people for no good reason are commonly and rightly regarded as dickheads.

"Extremism" as a concept shouldn't have a place in government policy. It's not any more analytically valid than "bad shit" or "bollocks". It is, first and foremost, a term of polemical censure – a word we conventionally use to register our disapproval of viewpoints and preferences that contradict our own. The government defines "extremism" as anything that stands opposed to fundamental British values of tolerance and mutual respect. ISIS clearly fits into this category, as does a whole range of other groups and individuals. ISIS, in turn, no doubt sees the British government as extreme: the antithesis of its own godly values. Indeed, ISIS is currently at war against extremism, as it defines it, in the areas under its control, violently policing the extreme activities of smoking, gambling, drinking, artistic creation and free sexual expression.

So extremism is anything we want it to be. It is also, more crucially, not the problem. Extreme views, however defined, do not kill or maim anyone. People do. Living, breathing, shitting human beings, armed with their fists and feet and anything they can get their hands on. This may sound completely banal and obvious, but the point seems to be lost on Cameron and his advisors.

No doubt they would counter that extreme views serve to prompt and justify terrorism, and thus provide an important causal context for its occurrence. But the reality is far more complex. As terrorism scholar John Horgan has observed, not all people with extreme views carry out acts of terrorism, and, conversely, not all those who commit terrorist acts are ideological true believers (i.e. extremists). "The idea that radicalisation causes terrorism is perhaps the greatest myth alive today in terrorism research," he writes. "[First], the overwhelming majority of people who hold radical beliefs do not engage in violence. And second, there is increasing evidence that people who engage in terrorism don't necessarily hold radical beliefs."

For some terrorists, as Jerrold Post – founder of the CIA's Center for the Analysis of Personalities and Political Behavior – once put it: "The cause [as in the ideology or the stated grievance] is not the cause [as in "root"]"; on the contrary, the violence, drama and sense of belonging and purpose is." Horgan rightly insists that the task of counter-terrorism policy is to stop the violent activities of terrorists, and that this – rather than focusing on de-radicalisation or the changing of "hearts and minds" – should be the main priority.

ISIS fighters on the border of Syria and Iraq

ISIS's ideology – and let's not pretend the government's proposals are about other forms of extremism, or other groups, despite the usual perfunctory noises about right-wing terrorism – must be countered. The group is a moral disgrace and has not even attempted to hide its myriad acts of inhumanity since its dramatic capture of large swathes of territory in Iraq and Syria last year. It must be rejected and refuted as the enemy of civilised norms that we all share and wish to live by.

But banning the speech of those who espouse its ideology or who utter words of sympathy for it is a fatal error, since this would not only be profoundly illiberal – a direct threat to the very values the Prime Minister is proclaiming to defend – but risk being counterproductive by further alienating those whose don't share or reject liberal democratic values.

The best way to counter contemptible viewpoints is to let their adherents vent them, and then carefully and comprehensively rip those views apart. Ideally, this should be done in a public forum, so as to expose the reprehensible views in question to maximum shame. This is all straight out of John Stuart Mill's classic defence of liberalism, On Liberty, and it's a viewpoint as valid today as it was when it was first published in 1859.

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A very stupid way to counter contemptible viewpoints is to ban their adherents from venting them. This not only risks giving the adherents a kind of counter-cultural glamour they formerly lacked, but may also provoke a further hardening of their views, or even a violent reassertion on the part of the adherents themselves (or those who take offence on their behalf).

The real issue for counter-terrorism is not extremism, but extreme action. It is those who walk the walk, not noisy blowhards and similar belligerents. It is actual terrorists and their plots we should be concerned about and try to stop. Outlawing a set of views won't stop anyone from having them, so that plan of action only serves to divide and marginalise. But the government, despite all their resources and expertise, do not seem to recognise this. Instead, they choose to follow a path that may well backfire, worsening the very same concern they seek to contain.